(Refer to the detailed answer for 68d3d1916afe1c7ad70ac91e.)

• The system must be suitable for the protected space (machinery spaces, cargo spaces, pump rooms, electrical spaces) and use an approved extinguishing medium (CO2, inert gas, or a clean agent).
• The quantity of the extinguishing medium must be sufficient to extinguish a fire in the largest protected space (e.g. CO2 at the required percentage of the gross volume).
• The system must be capable of being discharged quickly (e.g. at least 85% of the CO2 within 2 minutes) and distributed uniformly through the space.
• The controls must be arranged so that the system cannot be discharged accidentally, and so that personnel are warned (an alarm) before discharge; the controls are located outside the protected space.
• The system must be installed so that the protected space can be sealed (ventilation, skylights, doors closed) to retain the gas.
• The system must be tested, maintained and the crew trained in its use.
• The storage of the gas (cylinders) must be outside the protected space, in a suitable location, protected from heat.

• Quantity: For machinery spaces, the quantity of free CO2 must be at least 40% of the gross volume of the space (for spaces up to 2000 m3) and 35% of the gross volume for larger spaces (plus the casing), or as specified by the FSS Code; for cargo spaces, at least 30% of the gross volume. At least 85% of the required quantity must be discharged within 2 minutes.
• Piping: The distribution piping must be of suitable size and material, run into the protected space with nozzles arranged to distribute the gas uniformly (nozzles near the top and a pair near the bilge/bottom); the piping is pressure-tested (e.g. 1.5x working pressure) and has no dead-ends.
• Controls: Two independent controls (a main control and a section/quick-release valve), arranged so that a person can operate the system; the controls are located outside the protected space (a release cabinet), with a two-stage operation (first an alarm, then the discharge); a pressure gauge, safety/relief valve, and non-return valves are fitted.
• Volume of free CO2: The "free CO2" is the volume of CO2 gas that would be produced from the liquid CO2 in the cylinders; the quantity is calculated to give the required percentage of the gross volume of the protected space.
• Maintenance: Weekly/monthly checks of the cylinder pressures and leak tests, valve operation, alarm tests, piping/nozzle inspection; periodic (e.g. 5-yearly or per the approved schedule) discharge/test and hydrostatic test of the cylinders; inspection of the release mechanism; and the system is serviced by an approved station. All tests are recorded.